Steps to Reproduce the issue:
1.  Create a viewport in a layout that is zoomed into a certain area in model space.
2.  Lock the viewport.
3.  Change to model space within that layout.
4.  LandXML import or data shortcut create reference an object into the drawing.

What is the problem?
The locked viewport "zooms to extents" of the object imported.  You have to unlock the viewport, fix it, then lock it again.

What were the expected results?
Create the object without zooming extents or switch to model tab before importing object.  Adding a warning about switching to Model tab with cancel option would be even better.

Submitted By: TommieR
Autodesk Service Request: SR#:1-3618052751
First Appeared: Civil 3D 2008
Status as of 2008 SP2: Still reproducible
Status as of 2009: Still reproducible